Amperometric detection decoupling

Simple etching of the capillary end served to decouple the electrophoretic current from that of amperometric detection, permitting quantitation of attomole levels of catecholamines from brain microdialyzates.24 A postcolumn reactor using bromine generated electrochemically in situ has been used in the detection of peptide thiols, such as glutathione and cysteine, separated by capillary electrophoresis.25... 

C. -C. Wu, R.-G. Wu, H.-G. Huang, Y.-C. Lin and H.-C. Chang, Three-electrode electrochemical detector and platinum film decoupler integrated with a capillary electrophoresis microchip for amperometric detection., Anal. Chem., 75 (2003) 947-952. 

D. -C. Chen, F.-L. Hsu, D.-Z. Zhan and C.-H. Chen, Palladium film decoupler for amperometric detection in electrophoresis chips, Anal. Chem., 73 (2001) 758-762. 

J. Vickers and C.S. Henry, Simplified current decoupler for microchip capillary electrophoresis with electrochemical and pulsed amperometric detection, Electrophoresis, 26 (2005) 4641-4647. 

C. -Ch.J. Lai, Ch.-h. Chen and F.-H. Ko, In-channel dual-electrode amperometric detection in electrophoretic chips with a palladium film decoupler, J. Chromatogr. A, 1023 (2004) 143-150. 

A Pd film decoupler has also been constructed for amperometric detection of catecholamines. The Pd film has been thermally evaporated onto a plastic chip (without the use of the Cr or Ti adhesion underlayers). Owing to the fast diffusion of H2 on a Pd surface, gas bubbles will not form. Pd is able to absorb H2 produced at the cathode up to a Pd/H ratio of 0.6. This reduces one of the interferences to the EC signal, leading to an improvement of LOD to 0.29 pM dopamine [205,375]. With an optimal decoupler size of 500 pm, up to 6 h of operation was achieved with an electric field of 600 V/cm [375]. 

It was reported that in-channel amperometric detection was possible without using a decoupler. This has been achieved using an electrically isolated (non-grounded, floating) potentiostat [750]. On the other hand, when the CE power supply was battery operated (12-V battery to power 3-kV HV module) and therefore it was electrically isolated from the electrochemical detection system [765], In another report, a portable HV power supply (using 6 V battery for the HV module and 9 V battery for the electrochemical detection circuit) was constructed for CE-EC detection on a glass chip [751],... 

In amperometric detection, there is H2 evolution at the electrode. How can this problem be prevented by using a Pd decoupler near the grounded cathode [205] (2 marks)... 

Three-electrode electrochemical detector and platinum film decoupler integrated with a capillary electrophoresis microchip fin amperometric detection. Anal Chem 75 947-952... 

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